80 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [ Dec. 8, 
form—some examples being almost circular, while others are trans- 
versely oval. WV. Vicaryi is not rare in certain pebbles, no less 
than thirty-five specimens, representing different ages, having been 
found by Mr. Vicary. It bears also some resemblance to NV. ventri- 
cosa, Hall, and is probably of Silurian age, for it has been found 
associated with impressions of an Orthis much resembling O. redux. 
In America JV. elegans belongs to the Lower Helderberg rocks. An 
allied form JV. (S.) pesum, Sow., is not rare in our British Upper 
Silurian strata. 
14. Aruyris IncERTA, n. sp.? PI. IV. fig. 12. 
More or less pentagonal, rather wider than long; dorsal valve 
moderately convex ; surface smooth, with a broad, slightly produced 
mesial fold, flattened or depressed along the middle; ventral valve 
convex; sinus shallow. Length 6, width 8 lines. 
Of this species only one or two internal casts of the dorsal valve 
and an external impression have been met with by Mr. Vicary; it 
is therefore impossible, with such scanty materials, to even hint at a 
definite specific identification. It much resembles certain small De- 
vonian specimens of 4. concentrica, and also the Carboniferous A. am- 
bigua, Sow. Some indeterminable impressions of an Orthis and of 
Tentaculites have been found along with it in the same pebble. 
Internal casts of two more species, perhaps referable to this genus, 
have been found. They are not, however, sufficiently complete to 
admit of being specifically determined ; but, for the sake of reference, 
I must give them a provisional denomination. 
15. AtHyRis? BUDLEIGHENSIS, n. sp.? Pl. IV. fig. 14. 
Of this species the internal cast of a ventral valve has alone been 
discovered; it is almost circular, slightly wider than long—no 
markings being observable but two slits in the beak, due to dental 
plates. It measures, length 9, and width 9} lines, and was found by 
Mr. Vicary along with Spirifera Verneuilii and Rhynchonella inaurita. 
It is consequently a Devonian species. 
16. ArHyris? ERRATICA, n. sp. Pl. LV. fig. 13. 
Shell small, elongated, oval; valves moderately convex. Length 4, 
width 3, depth 2 lines. 
The internal cast of one specimen was found by Mr. Vicary; we 
are not acquainted with its exterior. 
17. RKuYNCHONELLA INAURITA (Sandberger). Pl. V. figs. 1-3. 
Brach. rheinischen Schicht. in Nassau, p. 41, pl. xxxiii. fig. 5, 1855. 
Rhynchonella?, Salter, Quart. Journ. Geol. Soc. vol. xx. p. 296, 
pl. xvi. fig. 15. 
Subtrigonal, wider than long, both valves convex; dorsal valve 
gibbous ; mesial fold rising abruptly with greater or less width, and 
forming in profile a regular convex curve. In the ventral valve the 
sinus is broad and moderately deep, extending from the extremity 
of the beak to the front; beak incurved. Surface of each valve 
